I agree with much of what has already been said. I think it's a symptom of people's inability to understand the idea of platonic love or real friendship anymore. It seems like this is especially the case in America, as Boro says, and I find it incredibly sad: people who can't comprehend the idea of love that is not romantic/sexual are missing so much in life. I also think a lot of the giggling, in the case of teens, is an attempt to fit in and not necessarily a reflection of their feelings. I seem to recall (when I was a teenager, at least) the 'naughtiest' ideas being, somehow the safest; they put you in a position of power, while appearing naive is a fate worse than death!
